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    <title>Document</title>
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    <script>
        // for...in一般用来循环对象获取对象属性 for ... of循环数组获取值


        var obj = {
            name: '张三',
            age: 20,
            tel: 110
        }
        var arr = [1, 2, 3] 

        for(let key in arr) {
            console.log(key)
        }

        for(let value of  Object.keys(obj)) {
            console.log(value)
        }
    </script>
</body>
</html>